Upstate Freshwater Institute

Syracuse, NY, United States

Upstate Freshwater Institute

Syracuse, NY, United States

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Peng F.,Upstate Freshwater Institute | Peng F.,USG Corporation | Effler S.W.,Upstate Freshwater Institute
Limnology and Oceanography | Year: 2017

Characterization of autochthonously produced calcite particles, along with the associated heteronuclei, and evaluation of their effects on light scattering, are advanced for lacustrine waters. This is supported by (1) direct measurement of minerogenic particle populations from 12 northeastern U.S. lakes with scanning electron microscopy interfaced with automated image and X-ray analyses (SAX), and (2) application of the previously tested SAX−Mie-theory approach to resolve the contributions of calcite vs. allochthonous minerogenic particles to particulate scattering and backscattering coefficients (bp and bbp), and (3) comparison with organic contributions estimated through empirical bio-optics models. Intervals of substantial contributions of calcite to bp and bbp, described as “whiting events,” are demonstrated for these study lakes. Organic particles, apparently from two size ranges, likely corresponding to pico- and nanocyanobacteria, are found to serve as the primary heteronuclei for the calcite precipitation. The coating of these particles with calcite within the upper waters of the study lakes remained thin. The calculated relative increases in bbp were substantially more than for bp because of the greater effect of the higher refractive index (i.e., n) of calcite for the former. Differences in n values for calcite reported in the literature are a source of noteworthy uncertainty in associated bbp estimates. Nine years of spring−fall monitoring in Cayuga Lake, New York, documented major interannual variations in the whiting events with respect to timing, magnitude of the scattering signatures, and the sizes of heteronuclei. Whiting events can have major effects on commonly monitored optical features, including Secchi depth and remote sensing reflectance. © 2016 Association for the Sciences of Limnology and Oceanography


Lee Z.,University of Massachusetts Boston | Pahlevan N.,University of Massachusetts Boston | Ahn Y.-H.,Korea Advanced Institute of Science and Technology | O'Donnell D.,Upstate Freshwater Institute
Applied Optics | Year: 2013

It has been a long-standing goal to precisely measure water-leaving radiance (Lw, or its equivalent property, remote-sensing reflectance) in the field, but reaching this goal is quite a challenge. This is because conventional approaches do not provide a direct measurement of Lw, but rather measure various related components and subsequently derive this core property from these components. Due to many uncontrollable factors in the measurement procedure and imprecise post-measurement processing routines, the resulting Lw is inherently associated with various levels of uncertainties. Here we present a methodology called the skylight-blocked approach (SBA) to measure Lw directly in the field, along with results obtained recently in the Laurentian Great Lakes. These results indicate that SBA can measure Lw in high precision. In particular, there is no limitation of water types for the deployment of SBA, and the requirement of post-measurement processing is minimum; thus high-quality Lw for a wide range of aquatic environments can be acquired. © 2013 Optical Society of America.


Peng F.,Upstate Freshwater Institute | Effler S.W.,Upstate Freshwater Institute
Journal of Great Lakes Research | Year: 2010

Light-scattering attributes of minerogenic particles from the water column of the western basin of Lake Erie (13 sites, plus one from the central basin and one from Sandusky Bay), collected after a wind event, were characterized by scanning electron microscopy interfaced with automated image and X-ray analyses (SAX). SAX results specified scattering attributes for individual particles, including size and chemical composition, and were used in forward Mie theory calculations of minerogenic scattering and backscattering coefficients (bm and bb,m). Clay mineral particles, in the size range of 1-20μm, were the dominant form of minerogenic scattering, representing >75% of bm and bb,m. Levels of bm and bb,m were high in the western basin, apparently in part due to wind-driven sediment resuspension, and wide spatial variability was observed. The credibility of the SAX-Mie estimates of bm and bb,m was supported by the extent of optical closure obtained with paired bulk measurements of particulate scattering and backscattering coefficients (bp and bbp), and independent estimates of organic particle contributions based on empirical bio-optical models. Minerogenic particles dominated bp and particularly bbp, and regulated spatial differences in the related common metrics of optical water quality, including turbidity and clarity. The bbp:bp ratio was found to be a good predictor of the spatial differences in the relative contributions of minerogenic particles versus phytoplankton to scattering. © 2010 International Association for Great Lakes Research.


Gelda R.K.,Upstate Freshwater Institute | Effler S.W.,Upstate Freshwater Institute | Peng F.,Upstate Freshwater Institute
Journal of Environmental Engineering (United States) | Year: 2012

High loads of inorganic particles received following runoff events from terrigenous sources can cause elevated turbidity (Tn) levels in water supply lakes and reservoirs. The development, successful testing, and application of a mechanistic Tn model is documented for Kensico Reservoir, New York, the terminal reservoir of New York City's multireservoir unfiltered water supply, where a standard of Tn<5 nephelometric turbidity units (NTU) must be met in the withdrawals. The model includes three submodels: (1) hydrothermal/transport; (2) turbidity; and (3) alum floc deposition. The alum floc deposition submodel supports simulation of the extent of local deposits formed from alum additions made to reduce high Tn delivered from extreme runoff events. The modeling is supported by long-term monitoring of the inflows, reservoir, and withdrawals, characterization of the turbidity-causing particles (mostly clay minerals, 1-10-μm in diameter), resolution of specific conductance (tracer) patterns with rapid profiling instrumentation, and characterizations of the alum floc deposits. The two-dimensional hydrothermal/transport and Tn submodels are demonstrated to perform well in both long-and short-term simulations. Predictions of extent and magnitude of the alum floc deposits are shown to be consistent with the available information. Application of the tested model establishes violations of the Tn standard that would have occurred for extended intervals without the alum additions. The volume of the in-reservoir floc deposit formed from this practice is estimated. © 2012 American Society of Civil Engineers.


Effler S.W.,Upstate Freshwater Institute | Peng F.,Upstate Freshwater Institute
Fundamental and Applied Limnology | Year: 2012

The dynamics of light scattering attributes of minerogenic particles in the upper waters of an urban lake, Onondaga Lake, NY, U.S.A., are characterized for the spring-summer interval of 2010 with scanning electron microscopy interfaced with automated image and X-ray analyses (SAX). SAX results are used to estimate the minerogenic scattering coeffi cient (bm) through Mie theory calculations. Good optical closure of the summation of bm and organic particle scattering (bo), the latter estimated by empirical bio-optical models based on the concentration of chlorophyll-a, with paired bulk measurements of particulate scattering (bp) is demonstrated. The average of the ratio of (bm + bo) to bp was 1.07; the average percent difference between this summation and bp was 21 %. The contribution of bm to bp ranged fro m ~5 % during a dry weather interval to 70 % following a runoff event; the overall average, for the relatively low runoff study year, was nearly 25 %. Allochthonous clay mineral particles were the dominant minerogenic component, primarily responsible for the observed dynamics in bm. Calcium carbonate containing particles, with nuclei as clay minerals primarily and organic particles secondarily, were the second most important contributor to bm. Particles in the size range of 1-10 μm were responsible for bm during low tributary fl ow intervals, but particles > 10 μm became important following high runoff events. A strong inverse relationship between Secchi depth and bp prevailed, coupling this fundamental metric of water quality to the contributions of the various light scattering constituents. The light scattering and clarity conditions of the lake are considered in the context of prevailing and potential future driving conditions. © 2012 E. Schweizerbart'sche Verlagsbuchhandlung, Stuttgart, Germany.


Peng F.,Upstate Freshwater Institute | Effler S.W.,Upstate Freshwater Institute
Applied Optics | Year: 2012

The relationship between the particulate scattering coefficient (b p) and the concentration of suspended particulate matter (SPM), as represented by the mass-specific scattering coefficient of particulates (b *p bp/SPM), depends on particle size distribution (PSD). This dependence is quantified for minerogenic particle populations in this paper through calculations of b* p for common minerals as idealized populations (monodispersed spheres); contemporaneous measurements of bp, SPM, and light-scattering attributes of mineral particles with scanning electron microscopy interfaced with automated image and x-ray analyses (SAX), for a connected stream-reservoir system where minerogenic particles dominate b p; and estimates of bp and its size dependency (through SAX results-driven Mie theory calculations), particle volume concentration, and b*p . Modest changes in minerogenic PSDs are shown to result in substantial variations in b*p . Good closure of the SAX-based estimates of bp and particle volume concentration with bulk measurements is demonstrated. Converging relationships between b*p and particle size, developed from three approaches, were well described by power law expressions. © 2012 Optical Society of America.


Effler S.W.,Upstate Freshwater Institute | Peng F.,Upstate Freshwater Institute
Limnology and Oceanography | Year: 2014

The dynamics of light scattering by minerogenic particles in the upper waters of Cayuga Lake, New York, were characterized for the spring-autumn interval of 8 yr (1999-2006) at pelagic and nearshore sites with a scanning electron microscope interfaced with automated image and x-ray analyses (SAX). SAX results were used to estimate the minerogenic scattering coefficient (bm) through Mie theory calculations. SAX-Mie supported a two-component model for particulate scattering (bp) that included an organic component of scattering (bo), estimated from a bio-optical model. The credibility of the bm estimates and the two-component modeling approach was demonstrated through good closure of the modeling results with bulk values of bp(estimated from measurements of the beam attenuation coefficient at 660 nm). The average of the ratio bp: (bm + bo) was 1.03 (average relative error 19.4%). Two minerogenic particle types were important in regulating the dynamics of bm-clay minerals that increased in concentration in response to runoff events, and calcium carbonate precipitated mostly on small organic particles during short-term late-summer whiting events. bm was attributed to particles in the size range of 1-10 μm. Variations in bm dominated the overall variations in bp and Secchi disk depth; differences in bo explained well those observed in bp during dry weather intervals of low bm. Higher bm values, mainly associated with clay mineral particles, were observed at the nearshore site as opposed to the pelagic location; there was a positive linkage between these levels and tributary flow rate. © 2014, by the Association for the Sciences of Limnology and Oceanography, Inc.


Peng F.,Upstate Freshwater Institute | Effler S.W.,Upstate Freshwater Institute
Limnology and Oceanography | Year: 2013

The light-absorbing attributes of minerogenic particle populations were determined for clay-mineral-enriched conditions at 14 sites in the western basin of Lake Erie following a wind-driven re-suspension event. Estimates of spectral absorption properties of the minerogenic particle assemblages, namely the imaginary part of the refractive index (n ′), the mean absorption efficiency factor (< Q a,m>), the mean package effect index (<>), and the mass-specific absorption coefficient (), are presented. These were based on laboratory measurements of non-algal particulate absorption (a NAP), minerogenic particle size distributions (PSD) with an individual particle analysis technique, and iterative Mie theory calculations to retrieve n ′(λ). There were wide spatial differences in magnitudes of these estimates. The n ′(λ) values are generally consistent with those obtained with a different methodology. Absorption by minerogenic particles was dominated by clay mineral particles in the 2-20 μm size range. The effects of n ′ and PSD variations on both < Q a,m> and <> were well-parameterized in the multiplicative format of optical thickness, and were qualitatively consistent with the literature and Mie theoretical predictions for monodispersed spheres. Spatial differences in n ′ and PSD were both important drivers of the variations in < Q a,m> and <>. Mie theory calculations indicate that absorption by these minerogenic particles causes substantial decreases in their spectral scattering, backscattering, and backscattering ratio, from the red to the blue spectral regions, relative to the case of non-absorbing. © 2013, by the Association for the Sciences of Limnology and Oceanography, Inc.


Peng F.,Upstate Freshwater Institute | Effler S.W.,Upstate Freshwater Institute
Limnology and Oceanography | Year: 2016

The particulate scattering and backscattering coefficients (bp and bbp) were partitioned into the additive contributions of minerogenic (bm and bb,m) and organic (bo and bb,o) components for nearshore and pelagic areas of Cayuga Lake, New York, over a 7 month period in 2013. The analysis was based on paired measurements of (1) bulk bp and bbp, (2) light-scattering properties of mineral particles, with an individual particle analysis (IPA) technique, and (3) concentrations of chlorophyll a ([Chl]) and particulate organic carbon (POC), as two indices to quantify organic particle scattering. bm and bb,m were estimated through Mie theory calculations with IPA results as inputs. bo and bb,o were estimated with both system-specific and oceanic bio-optical models parameterized on [Chl] or POC. POC performed better than [Chl] as the index for both bo and bb,o. The averages of the ratios (bm+bo) : bp and (bb,m+bb,o) : bbp at 660 nm, were 1.02 and 1.03, respectively; the average relative errors were 18.2% and 15.6%. Multiple empirical bio-optical models developed for Case 1 oceanic waters (for bo and bb,o estimates) approached the closure performance of the system-specific relationships. In addition to systematically accounting for more bbp than bp, terrigenous minerogenic particles made greater contributions to both bp and bbp in the nearshore area proximate to tributary inputs than in pelagic waters. A strong positive dependency of the backscattering ratio (bbp : bp) on the bm : bp ratio was observed for both nearshore and pelagic areas. © 2016 Association for the Sciences of Limnology and Oceanography.


Peng F.,Upstate Freshwater Institute | Effler S.W.,Upstate Freshwater Institute
Journal of Great Lakes Research | Year: 2011

Light-scattering attributes of minerogenic particles from the upper waters of Lake Ontario, collected lake-wide from pelagic waters in late 2007 summer and early 2008 spring cruises and over the summer interval at a near-shore site in 2008, were characterized by scanning electron microscopy interfaced with automated image and X-ray analyses (SAX). SAX results were used to estimate minerogenic scattering and backscattering coefficients (bm and bb,m) through Mie theory. Two minerogenic particle regimes with respect to light scattering were resolved: (1) clay mineral dominance and (2) dominance by 'whiting' (CaCO3 precipitate) in late summer in portions of the lake. Clay minerals made noteworthy and important contributions to overall particulate scattering and backscattering coefficients (bp and bbp, respectively) in spring and early summer. Dramatic increases in values of bp, and particularly bbp, as well as decreases in Secchi disk depth (SD), were observed during whiting from the associated large increases in bm and bb,m. Features of these events were the primary drivers of the spatial patterns in late summer and temporal differences observed for scattering and SD. Particles in the size range of 1-10μm were responsible for minerogenic scattering during stratification, but those with sizes >10μm made noteworthy contributions at certain sites during spring turnover. The credibility of the SAX-Mie estimates of bm and bb,m was supported by the extent of optical closure obtained with paired bulk measurements of overall bp and bbp (2007 summer cruise), and independent estimates of organic particulate scattering and backscattering through empirical bio-optical models. © 2011 International Association for Great Lakes Research.

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